As is known in the art of water treatment for microbiological control, a deficiency of chlorine, of hypochlorites, and of certain halogenated organic water-treating agents is the formation, during usage, of undesirable disinfection by-products. These by-products are undesirable both from the standpoint of environmental concerns and also from the standpoint of toxicological considerations.
Certain 1,3-dihalo-5,5-dialkylhydantoins have been found to be effective as biocides for aqueous systems such as industrial cooling water, recreational water, and wastewater.
Persons using biocidal agents in the biocidal treatment of water customarily, if not universally, refer to “free chlorine” level as a measure of biocidal control. To achieve “free chlorine” levels in water treatment, solid materials are often preferred because of their high weight percent activity. N,N′-bromochloro-5,5-dimethylhydantion (BCDMH) has been one of the most widely-used solid sources of “free chlorine” for water treatment. One of the features emphasized for BCDMH by suppliers of BCDMH is that in use, the combined chlorine from the biocide regenerates “free chlorine” by reaction with inactive bromide species formed during the water treatment operation. In other words, the chlorine atom in the initial N,N′-bromochloro-5,5-dialkylhydantoin is said to be a precursor for additional “free chlorine” for sanitation purposes.
In use, BCDMH hydrolyzes into HOBr and HOCl both of which register as “free chlorine” species in commonly-used standard test procedures. These methods for determining “free chlorine” levels in treated water, involve use of a reagent known as DPD (i.e., N,N′-diethyldiphenylenediamine) and a buffer, and the results of such analyses are commonly used, if not universally used, as the basis for determining the quantity of a halogen-containing microbiocidal agent to be used for water treatment. Heretofore, consumers of BCDMH have only been concerned with the level of “free chlorine” provided by a given quantity of that biocidal material. What has not been realized by such consumers is the amount of “total chlorine” being utilized in order to achieve the requisite “free chlorine” level. As a consequence, the consumer has not had available a yardstick by which to determine the true economic efficiency of using BCDMH as a biocidal agent in the treatment of water. To achieve optimum economic efficiency, the consumer should have available for use a biocidal agent in which the amount of “free chlorine” released into the water corresponds closely to the “total chlorine” content of the biocidal agent.
In the event a biocidal agent provides a relatively small amount of “free chlorine” in relation to its “total chlorine” content, it has been deemed necessary to utilize a relatively large amount of such agent in order to achieve microbiological control. This in turn means high levels of halogenated materials are released into the environment. If on the other hand, a biocidal agent could provide to the water an amount of “free chlorine” that closely corresponds to the “total chlorine” content of the biocidal agent, effective microbiological control could be realized by use of much smaller dosages and with consequent minimal adverse impact upon the environment.